diff --git a/tools/profiler/LulCommon.cpp b/tools/profiler/LulCommon.cpp
index 86c3e500e58..9664230ee3c 100644
--- a/tools/profiler/LulCommon.cpp
+++ b/tools/profiler/LulCommon.cpp
@@ -72,7 +72,7 @@ Module::~Module() {
 //
 class UniqueString {
  public:
-  UniqueString(string str) { str_ = strdup(str.c_str()); }
+  explicit UniqueString(string str) { str_ = strdup(str.c_str()); }
   ~UniqueString() { free(reinterpret_cast<void*>(const_cast<char*>(str_))); }
   const char* str_;
 };
diff --git a/tools/profiler/LulMain.cpp b/tools/profiler/LulMain.cpp
index 6e6c1d235f1..0384afc8f48 100644
--- a/tools/profiler/LulMain.cpp
+++ b/tools/profiler/LulMain.cpp
@@ -490,7 +490,7 @@ class SegArray {
 
 class PriMap {
  public:
-  PriMap(void (*aLog)(const char*))
+  explicit PriMap(void (*aLog)(const char*))
     : mLog(aLog)
   {}
 
@@ -838,7 +838,7 @@ class PriMap {
 class CFICache {
  public:
 
-  CFICache(PriMap* aPriMap) {
+  explicit CFICache(PriMap* aPriMap) {
     Invalidate();
     mPriMap = aPriMap;
   }
diff --git a/tools/profiler/LulMain.h b/tools/profiler/LulMain.h
index ec84d43882d..ac97a908f9f 100644
--- a/tools/profiler/LulMain.h
+++ b/tools/profiler/LulMain.h
@@ -60,7 +60,7 @@ namespace lul {
 class TaggedUWord {
 public:
   // Construct a valid one.
-  TaggedUWord(uintptr_t w)
+  explicit TaggedUWord(uintptr_t w)
     : mValue(w)
     , mValid(true)
   {}
@@ -165,7 +165,7 @@ class CFICache;
 class LUL {
 public:
   // Create; supply a logging sink.  Initialises the rw-lock.
-  LUL(void (*aLog)(const char*));
+  explicit LUL(void (*aLog)(const char*));
 
   // Destroy.  This acquires mRWlock for writing.  By doing that, waits
   // for all unwinder threads to finish any Unwind() calls they may be
diff --git a/tools/profiler/LulMainInt.h b/tools/profiler/LulMainInt.h
index 16cd391ab9f..5b795d65933 100644
--- a/tools/profiler/LulMainInt.h
+++ b/tools/profiler/LulMainInt.h
@@ -223,7 +223,7 @@ public:
   // so let's use mSummaryMinAddr == 1 and mSummaryMaxAddr == 0 to denote
   // this case.
 
-  SecMap(void(*aLog)(const char*));
+  explicit SecMap(void(*aLog)(const char*));
   ~SecMap();
 
   // Binary search mRuleSets to find one that brackets |ia|, or nullptr